The use of DNA or RNA identification is now widely accepted as a means of distinguishing between different cells or cell types or between variants of the same cell type containing DNA mutations. Applications such as human leukocyte antigen (HLA) typing, which are more commonly carried out by identification of characteristic surface antigens using antibodies, may alternatively be affected by identification of the DNA coding for such antigens. Microbial infection or contamination may be identified by nucleic acid analysis to detect the target organism, rather than relying on detecting unique features of the cells of the microorganisms, e.g., morphological or biochemical characteristics. Genetic variations may be identified by similar means.
Molecular characterization of pathogens such as bacteria, viruses, and fungi is currently achieved by isolation from total nucleic acid, followed by cloning and subsequent analysis, or amplification of full or partial genomic sequences by polymerase chain reaction (PCR). PCR is the more powerful technique due to its ability to recover viral sequences and whole genome components from very low viral titers, and is now the preferred approach for most applications. Currently, total viral and genomic nucleic acids are isolated from infected tissues by methods which involve multi-step protocols for DNA or RNA extraction, precipitation and purification.
A frequent limitation for studying viruses and other pathogens at the molecular level is the ability to reliably obtain high quality nucleic acids from material, such as biological samples. Samples, including blood samples, must be collected and preserved in order to maintain integrity of the nucleic acids until they can be processed. This poses challenges when sample numbers are large and when working in the field. Field studies are thus constrained by the resources required for sample preservation and transportation, placing restrictions on the number of samples that can be collected in a given time and the size and remoteness of the regions that can be effectively surveyed. Timely processing and/or storage of the samples before they spoil can also be problematic in locations where access to well-equipped laboratory facilities is limited.
Biomedical engineers have traditionally developed technologies in response to the needs of the developed world's medical community. As a result, existing diagnostic systems generally meet the requirements of well-funded laboratories in highly regulated and quality-assessed environments. However, such approaches do not address the needs of the majority of the world's people who are afflicted with infectious diseases, who have, at best, access to poorly resourced health care facilities with almost no supporting clinical laboratory infrastructure. A major challenge for the biomedical engineering community is to develop diagnostic tests to meet the needs of these people, the majority of whom are in the developing world.
Nucleic acid-based diagnostics generally require an initial nucleic acid isolation step to separate the nucleic acid from materials such as protein, which may interfere in the hybridization and amplification steps. A range of methods are known for the isolation of nucleic acids, but these rely on a complex series of extraction and washing steps and are time consuming and laborious to perform.
Some embodiments of the technology described herein are based upon the identification by the applicant that a need exists for a reliable, inexpensive, quick and simple way to isolate nucleic acids from cells in mixtures or environments where they may be present at low concentrations, as a preparative first step in isolating nucleic acids from target cells in nucleic acid based cell detection procedures.